Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH] powerpc/time: use feature fixup in __USE_RTC() instead of cpu feature. | Date | Mon, 26 Aug 2019 21:41:39 +1000 |
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Christophe Leroy <christophe.leroy@c-s.fr> writes: > sched_clock(), used by printk(), calls __USE_RTC() to know > whether to use realtime clock or timebase. > > __USE_RTC() uses cpu_has_feature() which is initialised by > machine_init(). Before machine_init(), __USE_RTC() returns true, > leading to a program check exception on CPUs not having realtime > clock. > > In order to be able to use printk() earlier, use feature fixup. > Feature fixups are applies in early_init(), enabling the use of > printk() earlier. > > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> > --- > arch/powerpc/include/asm/time.h | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-)
The other option would be just to make this a compile time decision, eg. add CONFIG_PPC_601 and use that to gate whether we use RTC.
Given how many 601 users there are, maybe 1?, I think that would be a simpler option and avoids complicating the code / binary for everyone else.
cheers
> diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/time.h > index 54f4ec1f9fab..3455cb54c333 100644 > --- a/arch/powerpc/include/asm/time.h > +++ b/arch/powerpc/include/asm/time.h > @@ -42,7 +42,14 @@ struct div_result { > /* Accessor functions for the timebase (RTC on 601) registers. */ > /* If one day CONFIG_POWER is added just define __USE_RTC as 1 */ > #ifdef CONFIG_PPC_BOOK3S_32 > -#define __USE_RTC() (cpu_has_feature(CPU_FTR_USE_RTC)) > +static inline bool __USE_RTC(void) > +{ > + asm_volatile_goto(ASM_FTR_IFCLR("nop;", "b %1;", %0) :: > + "i" (CPU_FTR_USE_RTC) :: l_use_rtc); > + return false; > +l_use_rtc: > + return true; > +} > #else > #define __USE_RTC() 0 > #endif > -- > 2.13.3
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